U.S. patent number 5,796,323 [Application Number 08/873,458] was granted by the patent office on 1998-08-18 for connector using a material with microwave absorbing properties.
This patent grant is currently assigned to TDK Corporation. Invention is credited to Yasushi Iijima, Takashi Ito, Makoto Kobayashi, Takahide Kurahashi, Taro Miura, Shigeyuki Nakajima, Fumio Uchikoba.
United States Patent |
5,796,323 |
Uchikoba , et al. |
August 18, 1998 |
Connector using a material with microwave absorbing properties
Abstract
A ground conductor and a signal conductor are provided in an
insulating magnetic body respectively. The insulating magnetic body
is a compound member that combines ferromagnetic metal particles
and an insulating resin. A signal transmission element, a connector
or a circuit board with high frequency stopping and low pass
characteristics which will ensure reliable absorption of high
frequency components in the high frequency range, can be
provided.
Inventors: |
Uchikoba; Fumio (Tokyo,
JP), Nakajima; Shigeyuki (Tokyo, JP), Ito;
Takashi (Tokyo, JP), Miura; Taro (Tokyo,
JP), Kobayashi; Makoto (Tokyo, JP),
Kurahashi; Takahide (Tokyo, JP), Iijima; Yasushi
(Tokyo, JP) |
Assignee: |
TDK Corporation (Tokyo,
JP)
|
Family
ID: |
27455150 |
Appl.
No.: |
08/873,458 |
Filed: |
June 12, 1997 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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645717 |
May 14, 1996 |
|
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409682 |
Mar 23, 1995 |
5594397 |
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Foreign Application Priority Data
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|
|
Sep 2, 1994 [JP] |
|
|
6-209586 |
Sep 2, 1994 [JP] |
|
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6-209587 |
Oct 5, 1994 [JP] |
|
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6-241640 |
Jan 24, 1995 [JP] |
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7-9333 |
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Current U.S.
Class: |
333/260; 333/206;
439/583 |
Current CPC
Class: |
H01P
1/20 (20130101); H01P 1/215 (20130101); H01P
3/006 (20130101); H01P 3/081 (20130101); H05K
1/0373 (20130101); H01P 3/085 (20130101); H05K
2201/086 (20130101); H05K 1/0216 (20130101); H05K
1/024 (20130101) |
Current International
Class: |
H01P
1/20 (20060101); H01P 3/08 (20060101); H01P
1/215 (20060101); H05K 1/02 (20060101); H01P
001/04 (); H01P 001/202 (); H01P 001/215 () |
Field of
Search: |
;333/22R,81A,181-185,202,204,206,238,243,246,260 ;439/86,88,608,583
;174/36,16SC,118,288 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Bogar et al., Miniature Low-Pass EMI Filters, Proc. of the IEEE,
vol. 67, No. 1, Jan. 1979, pp. 159-163..
|
Primary Examiner: Gensler; Paul
Attorney, Agent or Firm: Oblon, Spivak, McClelland, Maier
& Neustadt, P.C.
Parent Case Text
This is a Continuation of application Ser. No. 08/645,717, filed on
May 14, 1996, now abandoned, which is a Continuation of application
Ser. No. 08/409,682, Filed Mar. 23, 1995 now U.S. Pat. No.
5,594,397.
Claims
What is claimed is:
1. A connector for suppressing signal noise components above 1 GHz,
comprising:
an insulating magnetic body having an insulating resistance of
10.sup.9 ohms or more and including a compound member in which
ferromagnetic metal particles and an insulating resin are
mixed;
a cylindrically shaped signal conductor having a tensile property
and penetrating and being in contact with said insulating magnetic
body;
a cylindrically shaped ground conductor mounted on and being in
contact with said insulating magnetic body and having each of two
ends formed as one of a cable connector and a circuit system
connector wherein said ground conductor covers said insulating
magnetic body.
2. A connector according to claim 1, wherein said two ends form
threaded portions.
3. A connector according to claim 1, wherein said signal conductor
is provided with slits running from both ends of said ground
conductor toward the center.
4. A connector according to claim 1, wherein the particle diameter
of said ferromagnetic metal particles is within a range of 0.01
.mu.m to 100 .mu.m.
5. A connector according to claim 1, wherein the particle diameter
of said ferromagnetic metal particles is proportional to a skin
depth that allows high frequency magnetic fields within the range
of operating frequencies to enter said particles.
6. A connector according to claim 1, wherein the content of said
ferromagnetic metal particles is within a range of 30 vol % to 70
vol %.
7. A connector according to claim 1, wherein said insulating resin
is constituted of at least one of epoxy, phenol, rubber or acrylic.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electronic part using a
material with microwave absorbing properties. To be more specific;
the present invention relates to an electronic part that attenuates
frequency components in the high frequency range by absorption. The
term electronic part, as defined in the present invention,
includes, at least, a signal transmission element, a connector and
a circuit board.
2. Discussion of Background
A low frequency pass type (high frequency stopping type) signal
transmission element is typically a low pass filter. A typical low
pass filter in the prior art obtains the required filter
characteristics by taking advantage of differences in the frequency
characteristics between impedance matching and impedance
mismatching to reflect a signal that belongs to a frequency band in
the high frequency range. Because of this, the undesired frequency
component which has been reflected is sometimes returned to the
front of the filter, which may cause, for instance, an unexpected
oscillation within the circuit. An absorption type low pass filter
absorbs the undesired frequency component and it remedies the
problem described above, which is observed in a reflection type low
pass filter.
There are absorption type low pass filters already in the known
art. For instance, there is an absorption type low pass filter,
already in wide use, that uses ferrite; to be more specific,
ferrite beads. However, the frequency band that can be absorbed
with ferrite is in the frequency range below 2 GHz. This means
that, since the absorbing effect is not significant at
approximately 2 GHz or higher, transmission of signals in this
range is allowed.
Another approach is disclosed in U.S. Pat. No. 4,297,661 with a
high pass filter whose microstrip is constituted with ferrite. This
high pass filter takes advantage of the phenomenon that an
absorbing effect is generated in the low frequency range and not in
the high frequency range. However, this prior art technology, too,
does not suppress the undesired signal component in the high
frequency range of 1 GHz or higher by absorption.
Schiffres proposed a coaxial transmission line using ferrite in
IEEE Transaction on Electromagnetic Compatibility, EMC-6, 55-61,
1964. This coaxial transmission line, however, was designed mainly
for acquiring properties in the MHz band; transmission properties
and reflecting properties in the high frequency range of 1 GHz or
higher were not disclosed. It is assumed that signals in the high
frequency range of 1 GHz or higher are transmitted.
A combination of a non-magnetic material which has absorbing
qualities in the high frequency range and a ferrite for signal
removal by absorption in the high frequency range has been reported
as an attempt at signal removal. This approach includes the EMI
filter proposed by Schlicke in IEEE Spectrum, 59-68, 1967 and the
low pass type EMI filter proposed by Bogar in Proc. of IEEE 67
159-163 1979. In these filters, part of the insulator of the
coaxial filter is constituted by laminating ferrite and a
dielectric substance. In addition, Fiallo proposed, in his
doctorate thesis at Pennsylvania State University in 1993 and in
IEEE, Transactions on Microwave Theory Tech., MTT-42 1176, 1984, a
filter with a microstrip structure that combines a ferrite and a
dielectric substance. However, these prior art technologies require
a complex multiple layer structure.
U.S. Pat. No. 4,146,854 discloses an attenuating element that uses
ferrite beads and a wave absorbing body constituted of a metal and
resin or the like compound member. Also, Japanese Unexamined Patent
Publication 127701/1992 discloses technology that uses a wave
absorbing material for a part of a non-magnetic microstrip line.
However, in either case, the wave absorber or the wave absorbing
body merely plays an auxiliary role to suppress the high frequency
component which cannot be absorbed.
In addition, in U.S. Pat. No. 4,301,428, a wire or cable that
includes a conductive element with suitable electric resistance and
a magnetic absorbing mixture is disclosed. The conductive element
has a composite structure in which a non-conductive core
constituted of a resin or glass fiber is covered with a thin
conductive metal layer. The magnetic absorbing mixture is
non-conductive and covers the conductive element. However, since
imposing an electric resistance on the signal line causes
attenuation in the signal component as well as removal of the noise
component, it does not suit applications that handle, for instance,
micro signals. In addition, this prior art technology only
discloses a wire and makes no reference to a signal transmission
element.
Connectors pose a similar problem to that discussed in regard to
signal transmission elements. Generally, connectors have been
developed with the emphasis on achieving signal transmission with
low dissipation from low frequencies through the high frequencies.
Known connectors which satisfy such needs include the SMA3.5 mm
type, the SMA7 mm type, the BNC type and the N type. Each of these
connectors is usually constituted with one or more signal lines, a
ground line and is structured in such a manner that insulation is
achieved between signal lines and the ground by an insulator
constituted with a resin, such as acrylic or Teflon. The
characteristic impedance of the connector are determined by its
shape and the body constant of the resin. In many cases it is
50.OMEGA..
As explained earlier, connectors have been developed with the
emphasis on achieving signal transmission with low dissipation from
the low frequencies through the high frequencies. However, with the
recent advances in electronic technology, the advancement of
digitalization of electronic circuits and the rapid development
toward higher frequencies, the need for reducing high frequency
noise in the GHz bands has increased drastically. In order to
reduce the high frequency noise in the GHz bands, it is necessary
to provide a connector with a low pass function that achieves
removal of undesired high frequency components through absorption
in the high frequency range. Yet, reflecting upon this background
situation, it is obvious that it is extremely difficult to achieve
a connector that suppresses the undesired signal components in the
high frequency range of 1 GHz or higher through absorption.
The electronic part described above, which may be a signal
transmission element or a connector, is intended to be used as a
noise removal element only, a function that has no relation to the
original function of the circuit structure. By adding these
electronic parts to a circuit, frequency components in the high
frequency range can be attenuated through absorption. By adding an
attenuating factor that acts by absorption on frequency components
in the high frequency range to a circuit board that is normally
used when structuring an electronic circuit, in the form of an
electronic part, such as a signal transmission element, a connector
or the like, the onus on the rest of the circuit for attenuating
such high frequency components through absorption can be reduced.
There is even a possibility that electronic parts such as signal
transmission elements and connectors that are used strictly as
elements for noise removal, unrelated to achieving the original
function, can be omitted.
Various attempts have already been made to suppress radiation of
high frequency noise components to the outside of the circuit and,
at the same time, to prevent the entry of high frequency noise
components from the outside of the circuit, by shielding the
circuit board itself. One example of this is the electromagnetic
wave shielded printed circuit board described on page 155 of
Electronic Parts Catalogue '92 compiled by the Parts Management
Committee of the Japan Electronic Machinery Industry Association.
However, in this case, it is necessary to enclose the board with a
shielding layer, making the structure complex and, as a result, it
is difficult to apply it in a limited way, to specific circuits
formed on the circuit board. In addition, it is obvious when
reflecting upon the background situation, that it is extremely
difficult to achieve a circuit board that suppresses the undesired
signal components in the high frequency range of 1 GHz or higher
through absorption.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an electronic
part with high frequency stopping and low pass characteristics
which will ensure reliable absorption of high frequency components
in the high frequency range.
It is a further object of the present invention to provide an
electronic part with high frequency stopping and low pass
characteristics which ensures reliable absorption of high frequency
components at 1 GHz or higher.
It is a still further object of the present invention to provide an
electronic part with a simple structure.
It is a still further object of the present invention to provide an
electronic part which can make the best use of the magnetic
dissipating properties of ferromagnetic metal particles by allowing
a high frequency magnetic field to permeate the inside of the
ferromagnetic metal particles efficiently and thoroughly regardless
of the skin effect in ferromagnetic metals.
It is a still further object of the present invention to provide an
electronic part that achieves extremely small attenuation of the
signal component and can be used in applications that involve
handling micro signals.
In order to achieve the objects described above, the electronic
part according to the present invention comprises an insulating
magnetic body, at least one ground conductor and at least one
signal conductor. Each conductor is provided in the insulating
magnetic body, which is a compound member that combines
ferromagnetic metal particles and an insulating resin.
Since the electronic part according to the present invention is
provided with at least one ground conductor and at least one signal
conductor in the insulating magnetic body, an electronic part for
performing signal transmission is achieved by grounding the ground
conductor and inserting the signal conductor into the signal
transmission path in an application to a signal transmission
passage. Such an electronic part may be a signal transmission
element, a connector or a circuit board.
Ferromagnetic metal is a substance that demonstrates high magnetic
permeability and high magnetic dissipation factors over a wide
frequency range and has, at the same time, high conductivity, as is
obvious when we consider a typical example of metal iron. Because
of this, if it is used in a large stop, the magnetic dissipation
property of a ferromagnetic metal such as iron cannot be utilized
fully because, due to the skin effect, a high frequency magnetic
field will not penetrate the iron. Therefore, in the present
invention, a ferromagnetic metal is used in the form of particles.
By doing so, the magnetic dissipation of a ferromagnetic metal such
as iron can be effectively utilized by allowing the high frequency
magnetic field to penetrate deeply into the individual
ferromagnetic metal particles.
According to the present invention, the insulating magnetic body
includes an insulating resin and ferromagnetic metal particles. The
ferromagnetic metal particles are electrically insulated by the
insulating resin, which coexists in the insulating magnetic body,
so that no electric current can run among the particles. This
causes a magnetic dissipation in a state in which the individual
ferromagnetic metal particles are electrically independent of one
another, to achieve outstanding high frequency magnetic dissipation
over a wide frequency range.
As has been explained, according to the present invention, the
undesired high frequency components in the high frequency range
which are included in a signal passing through the signal conductor
can be reliably absorbed through the absorbing effect of the
insulating magnetic body. To be more specific, a low pass signal
transmission element which has the absorption effect (high
frequency stopping) in the high frequency band of 1 GHz or higher
and which passes signals that belong in the lower frequency bands
is achieved.
Also, the impedance can be maintained almost constant up to a
frequency of approximately 20 GHz and reflection can be kept at
approximately -10 dB.
Furthermore, the insulating magnetic body that absorbs high
frequency components is constituted of a compound member which
combines ferromagnetic metal particles and an insulating resin and
the ground conductor and the signal conductor are both provided at
the insulating magnetic body, achieving a very simple
structure.
With the electronic part according to the present invention, when
constituting the insulating magnetic body, ferromagnetic metal
particles with a particle size in the range of 0.01 .mu.m to 100
.mu.m can be used. When selecting the ideal particle size from the
aforementioned particle size range, one of the most desirable means
is to determine the particle size of the ferromagnetic metal
particles based upon a skin thickness which will allow a high
frequency magnetic field within the range of operating frequencies
to enter the inside of the particles. By doing so, the high
frequency magnetic field can be ensured to thoroughly permeate
virtually all of the ferromagnetic metal particles present in the
insulating magnetic body. As a result, almost all ferromagnetic
metal particles present in the insulating magnetic body contribute
to producing the magnetic dissipation, greatly improving the
efficiency of their use.
The ground conductor can be provided either on the surface of, or
inside the insulating magnetic body. If the ground conductor is to
be provided on the surface of the insulating magnetic body, it may
be provided either to enclose the insulating magnetic body or
not.
The signal conductor can be provided either by adhering it to the
surface of the insulating magnetic body or by embedding it in the
insulating magnetic body. The signal conductor may be linear,
curved or spiral. Which of the these structures should be used
depends upon the type of electronic part being manufactured.
If the signal conductor is to be formed in a spiral, it is
desirable to coil it in such a manner that each turn is wound ahead
at approximately equal intervals in the direction of the coil axis,
with the turning angle being constant throughout. With this
structure, even when an electrically long line is formed within a
limited volume, the magnetic fluxes generated in the individual
turns do not cancel out one another overall and, as a result, a
large inductance can be obtained which, in turn, provides a large
attenuating factor.
A spiral signal conductor may be coiled around an insulating
magnetic body other than the one which has been mentioned earlier,
for example, a ferrite magnetic body. In such a case, an absorption
type filter, which provides sufficient loss characteristics even in
a frequency band of 1 GHz or less is achieved.
In the connector according to the present invention, the
aforementioned signal conductor is provided in such a manner that
it passes through the insulating magnetic body. The aforementioned
ground conductor is mounted on the insulating magnetic body and is
electrically insulated from the signal conductor by the insulating
magnetic body. The insulating magnetic body is constituted of a
compound material that combines ferromagnetic metal-particles and
an insulating resin.
In the connector according to the present invention, the signal
conductor is provided in such a manner that it passes through the
insulating magnetic body. Thus, the signal line can be connected to
either one side or both sides of the terminal conductor. Since the
ground conductor is mounted on the insulating magnetic body and is
electrically insulated from the signal conductor by the insulating
magnetic body, a simply structured connector with the ground
conductor grounded and the terminal conductor insulated from the
ground conductor by the insulating magnetic body is achieved.
The type and particle size of the ferromagnetic metal particles
that are selected to constitute the insulating magnetic body and
their function and the type and effect of the insulating resin that
are selected to constitute the insulating magnetic body have been
already described. By choosing them in this manner, a connector
which is suited to be used for connecting a circuit that is exposed
to high frequency noise of 1 GHz or more, is achieved.
The circuit board according to the present invention includes at
least two conductors and an insulating magnetic body. The
conductors are provided on the two opposite sides of the insulating
magnetic body, so as to sandwich the insulating magnetic body. The
insulating magnetic body is constituted of a compound material that
combines ferromagnetic metal particles and an insulating resin. Of
the two conductors, one is used as a ground conductor and the other
is used as a signal conductor. In an actual operating state,
whichever conductor is not grounded is patterned as a signal
conductor.
In the circuit board according to the present invention, conductors
are provided on the two opposite sides of the insulating magnetic
body, so as to sandwich the insulating magnetic body. Consequently,
one of the conductors can be used as a ground conductor and the
other can be used as a signal conductor. In an actual operating
state, one conductor is grounded and is patterned as a ground
conductor and the other is patterned as a signal conductor so that
the whole can serve as a circuit board.
The type and particle size of the ferromagnetic metal particles
that are selected to constitute the insulating magnetic body and
their function and the type and effect of the insulating resin that
are selected to constitute the insulating magnetic body have been
already described.
With the circuit board according to the present invention, the high
frequency noise components which are included in a signal passing
through the signal conductor can be reliably absorbed through the
absorbing effect of the insulating magnetic body in the state in
which the conductors are already patterned to achieve a required
circuit pattern and the circuit parts already mounted. Thus, a
circuit board which is suited to be used in a circuit that is
exposed to high frequency noise of 1 GHz or higher, is achieved.
Moreover, the structure in which the ground conductor and the
signal conductor are provided on the insulating magnetic body
achieves a high degree of simplicity. It can be easily applied to
any circuit.
BRIEF DESCRIPTION OF THE DRAWINGS
These and other advantages, features and objects of the present
invention will be understood by those of ordinary skill in the art
referring to the annexed drawings, given purely by way of
non-limitative example, in which;
FIG. 1 is a perspective of the signal transmission element
according to the present invention;
FIG. 2 shows the frequency-complex magnetic permeability
characteristics of the iron-phenol resin compound member;
FIG. 3 shows the frequency-complex dielectric constant
characteristics of the iron-phenol resin compound member;
FIG. 4 shows the frequency-complex magnetic permeability
characteristics of the NiZn ferrite in the prior art;
FIG. 5 shows the frequency-complex dielectric constant
characteristics of the NiZn ferrite in the prior art
FIG. 6 shows the transmission characteristics when the iron-phenol
resin compound member is used;
FIG. 7 shows the transmission characteristics when the NiZn ferrite
in the prior art is used;
FIG. 8 shows the transmission characteristics when a compound
member constituted of the NiZn ferrite-rubber resin in the prior
art is used
FIG. 9 is a perspective of another embodiment of the signal
transmission element according to the present invention;
FIG. 10 is a perspective of yet another embodiment of the signal
transmission element according to the present invention;
FIG. 11 is a perspective of yet another embodiment of the signal
transmission element according to the present invention;
FIG. 12 shows the transmission characteristics of the signal
transmission element shown in FIG. 11;
FIG. 13 is a perspective of yet another embodiment of the signal
transmission element according to the present invention;
FIG. 14 shows the transmission characteristics of the signal
transmission element shown in FIG. 13;
FIG. 15 is a exploded and disbursed view of yet another embodiment
of the signal transmission element according to the present
invention;
FIG. 16 is a cross section of the signal transmission element shown
in FIG. 15;
FIG. 17 is a cross section of the signal transmission element shown
in FIG. 16 along line A17--A17;
FIG. 18 shows the signal transmission characteristics of the signal
transmission element shown in FIGS. 15 and 16;
FIG. 19 shows the magnetic permeability-frequency characteristics
of iron
FIG. 20 shows the skin depth-frequency characteristics of iron;
FIG. 21 is a perspective of yet another embodiment of the signal
transmission element according to the present invention with the
signal conductor included in the element exaggerated;
FIG. 22 is an external perspective view of the signal transmission
shown in FIG. 21;
FIG. 23 is a cross section of the signal transmission element shown
in FIGS. 21 and 22;
FIG. 24 is a diagram of the electrically equivalent circuit of the
signal transmission shown in FIGS. 21 to 23 according to the
present invention;
FIG. 25 shows the signal transmission characteristics of is the
signal transmission element shown in FIGS. 21 to 23 according to
the present invention;
FIG. 26 shows the reflection characteristics of the signal
transmission element shown in FIGS. 21 to 23 according to the
present invention;
FIG. 27 shows the reflection characteristics when shorting and
opening of the signal transmission element shown in FIGS. 21 to 23
according to the present invention;
FIG. 28 is a development elevation along the transmission line with
the signal transmission element shown in FIGS. 21 to 23 according
to the present invention regarded as a TEM transmission line;
FIG. 29 is a perspective of yet another embodiment of the signal
transmission element according to the present invention with the
signal conductor included in the element exaggerated;
FIG. 30 is a cross section of the signal transmission element shown
in FIG. 29;
FIG. 31 shows an example of an application in which the signal
transmission element shown in FIGS. 1, 9, 11 and 15 to 17, FIGS. 21
to 23 or FIGS. 29 and 30 is employed to achieve an improvement in
the outside band characteristics of the band pass filter which is
inserted in high frequency power amplifying circuit in a mobile
phone or the like;
FIG. 32 shows an example of an application in which the signal
transmission element shown in FIG. 1, FIGS. 9 to 11, FIGS. 15 to
17, FIGS. 21 to 23 or FIGS. 29 and 30 is employed as a filter for
removing undesired signals in an intermediate frequency amplifying
circuit;
FIG. 33 is a front elevation of the connector according to the
present invention;
FIG. 34 is a cross section through line A34--A34 in FIG. 33;
FIG. 35 is a front elevation of the circuit board according to the
present invention;
FIG. 36 is a side elevation of another embodiment of the circuit
board according to the present invention
FIG. 37 is a perspective of the circuit board according to the
present invention, and
FIG. 38 shows the transmission characteristics of the circuit board
shown in FIG. 37.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
First, the signal transmission element according to the present
invention is explained in reference to FIG. 1. This type of signal
transmission element is used, for instance, as a low frequency pass
absorption type filter. The signal transmission element according
to the present invention includes, at least, one ground conductor
1, at least one signal conductor 2 and an insulating magnetic body
3. The ground conductor 1 and the signal conductor 2 are provided
at the insulating magnetic body 3, separated by a gap. In the
signal transmission element shown in the FIG., the ground conductor
1 is provided on one surface of the insulating magnetic body 3 and
the signal conductor 2 is provided on another surface of the
insulating magnetic body 3.
The insulating magnetic body 3 is constituted of a compound member
in which ferromagnetic metal particles and an insulating resin are
mixed. The ferromagnetic metal particles should be, for instance,
fine particles of pure iron (carbonyl iron particles) which are
obtained by thermally decomposing carbonyl iron. When these iron
particles are hardened into an insulating substance, a member is
obtained that demonstrates high loss characteristics over the
millimeter wave range. Apart from iron, other metals such as nickel
and cobalt may be used for the ferromagnetic metal particles.
Furthermore, an amorphous alloy may be used for the ferromagnetic
metal particles. One metal may be used to constitute all of the
ferromagnetic particles or different metals may be used in
combination.
The insulating resin to be mixed with the ferromagnetic metal
particles is not restricted to any particular type, but it has been
confirmed that good characteristics are achieved with phenol, epoxy
and rubber resins. Here too, just one type may be used or different
types may be used in combination. When using iron for the
ferromagnetic metal particles, if the base material is composed of
relatively large particles, several different types of commercially
available iron particles may be sifted through mesh. By doing this,
different particle sizes ranging from 0.01 .mu.m to 100 .mu.m can
be selected.
Since the signal transmission element according to the present
invention is provided with at least one ground conductor 1 and at
least one signal conductor 2 in the insulating magnetic body 3, by
grounding the ground conductor 1 and inserting the signal conductor
2 into the signal transmission passage in a signal transmission
application, a signal transmission element for performing signal
transmission is achieved.
Since the insulating magnetic body 3 includes the ferromagnetic
metal particles, a high frequency magnetic field penetrates deeply
into the inside of the individual ferromagnetic metal particles and
the magnetic dissipation of a ferromagnetic metal such as iron can
be effectively utilized. In addition, the insulating magnetic body
includes an insulating resin as well as the ferromagnetic metal
particles. Consequently, the ferromagnetic metal particles are
electrically insulated by the insulating resin which coexists in
the insulating magnetic body 3 so that no electric current runs
among the particles. This causes a magnetic dissipation with
individual ferromagnetic metal particles in the state in which they
are electrically independent of one another, achieving a large high
frequency magnetic dissipation over a wide frequency range.
As has been explained, with the signal transmission element
according to the present invention, undesired high frequency
components in the high frequency range that are included in a
signal passing through the signal conductor 2 can be reliably
absorbed through the absorbing effect of the insulating magnetic
body 3. To be more specific, a low pass signal transmission
element, which has an absorbing effect (high frequency stopping) in
the high frequency band of 1 GHz or higher and which passes signals
in the lower frequency bands, is achieved. Also, the impedance can
be maintained almost constant up to a frequency of approximately 20
GHz and reflection can be kept at approximately -20 dB. These
characteristics make it suitable to be used as a low pass
filter.
Furthermore, the insulating magnetic body 3, which absorbs the high
frequency component, is constituted of a compound member which
combines ferromagnetic metal particles and an insulating resin with
the ground conductor 1 and the signal conductor 2 both being
provided at the insulating magnetic body 3, thereby achieving a
very simple structure.
The low pass and high frequency stopping mechanism in the signal
transmission element according to the present invention is as
described below. When the reflection coefficient of the element is
assigned .GAMMA. and the transmissivity is assigned T, the
reflection gain S11 (.omega.) and the transmission gain S21
(.omega.) in the transmission path are expressed with the following
formulae:
In the expressions above, .epsilon..sub.eff indicates the complex
effective dielectric constant of the material and .mu..sub.eff is
the complex effective magnetic permeability of the material. In
reality, form factors are added to the complex effective dielectric
constant and the complex effective magnetic permeability of the
material to obtain the complex effective dielectric constant
.epsilon..sub.eff and the complex effective magnetic permeability
.mu..sub.eff. Zo indicates the characteristic impedance of the
circuit.
First, in order to produce absorption in the high frequency range,
the transmissivity T must be close to 0. This requires that (.mu.
.epsilon.) be either an imaginary number or a negative real number.
In other words, if either one of, or both .epsilon. and .mu. have
an imaginary number component and, at the same time, the larger
that value, the larger the absorption in the transmission line.
This means that the dissipation coefficient (D) of the material is
large in the high frequency range.
Also, in order to reduce the reflection (reduce S11) over the
entire frequency range, the reflection coefficient .GAMMA. must be
close to 0. Accordingly, (.mu..sub.eff /.epsilon..sub.eff).sup.1/2
must be close to the characteristic impedance Zo over the entire
frequency range.
In the case of the absorption phenomenon caused by ferrite or the
like, the imaginary number component normally reaches 0 at
approximately 2 GHz and the transmissivity T approaches 1 in the
high frequency range. As a result, the low pass effect cannot be
achieved.
In contrast, the compound member used in the present invention
shows a prominent degree of absorption starting at about 1 GHz and
continuing up through 20 GHz and higher, together dielectric
absorption. Consequently, unlike in ferrite material, the
transmissivity T is close to 0 up to the high frequency range.
Generally, the real number components of the dielectric coefficient
.epsilon. and the magnetic permeability .mu. become reduced as the
frequency is lowered in the range where absorption occurs. Because
of this, when absorption is occurring, the characteristic impedance
Zo of the signal transmission element changes along with the
frequency and consequently, the reflection coefficient .GAMMA.
increases, to promote reflection.
However, with the compound member used in the present invention,
although the magnetic permeability becomes greatly reduced when the
frequency goes up, the dielectric constant, too, becomes reduced at
the same time. This, in turn, contributes to reducing the change in
impedance, resulting in reduced reflection. Therefore, a low pass
filter which yields a high frequency stopping effect through
absorption in the high frequency range is achieved and a signal
transmission element with reduced reflection is thus obtained.
Next, a manufacturing method for producing the signal transmission
element described above is explained in simplified terms. First, a
rectangular parallelopiped specimen approximately 10 mm long by 5
mm wide by 30 mm thick was formed by mixing ferromagnetic particles
and insulating resin and then pressing. The insulating resin was
then hardened by implementing a suitable thermal treatment on the
specimen to obtain a compound member. After the specimen was
adjusted to a thickness of 0.4 mm, the insulating magnetic body 3
was obtained through a cutting process. The resulting insulating
magnetic body 3 was 10 mm long, L1, 5 mm wide, W1 and 0.4 mm thick,
H1. The ground conductor 1 was formed over the entire surface of
one side of this insulating magnetic body 3 and, at the same time,
the signal conductor 2 was formed on the surface opposite the
surface with the ground conductor. The ground conductor 1 and the
signal conductor 1 may be formed by, for instance, vacuum
deposition. The electrode width of the signal conductor 2 was
adjusted to achieve an element characteristic impedance of
50.OMEGA.. Through this process, a signal transmission element with
a microstrip line structure, in which the width W2 of the line and
the length of the signal line were approximately 0.3 mm to 0.8 mm
and 10 mm respectively, was obtained.
In order to evaluate the characteristics of the signal transmission
element thus prepared, the transmission characteristics S11 and S21
of the insulating magnetic material according to the present
invention, which constitutes the insulating magnetic body 3, were
measured.
For evaluation, these measured values were then compared against
the transmission characteristics, S11 and S21, of the reference
samples which employ insulating magnetic materials of the prior
art. There were two types of samples used as reference examples,
i.e., in one sample, NiZn ferrite (high frequency ferrite material)
was used for the insulating magnetic material and in the other,
NiZn ferrite-rubber compound material was used.
We used a network analyzer HP8720C (manufactured by Hewlett
Packard) and a measuring gauge HP83040 (manufactured by Hewlett
Packard) in order to evaluate the signal transmission elements. In
order to measure the complex dielectric constant and the complex
magnetic permeability up to 1 GHz with an impedance analyzer
HP4291A (manufactured by Hewlett Packard) plane parallel plate
capacitors and toroidal cores were prepared with the insulating
magnetic materials described above. In the high frequency range of
1 GHz or over, the toroidal cores prepared using the insulating
magnetic materials described above were inserted in a jig (AIR LINE
HP85051-60007 manufactured by Hewlett Packard) and the measurements
were made with a network analyzer HP8720C (manufactured by Hewlett
Packard) using the software program HP85071A (manufactured by
Hewlett Packard).
FIG. 2 shows the complex magnetic permeability characteristics of
the iron-phenol resin compound member (iron 60 vol %, particle
diameter 2 .mu.m) and FIG. 3 shows the complex dielectric constant
characteristics of the iron-phenol resin compound member (iron 60
vol %, particle diameter 2 .mu.m). FIGS. 4 and 5 show the complex
magnetic permeability and the complex dielectric constant
characteristics respectively of the NiZn ferrite in the prior art.
In the FIGS., the horizontal axis indicates the frequency and the
vertical axis indicates the relative magnetic permeability .mu. or
the relative dielectric constant .epsilon. and the dissipation
factor D.
In the case of the iron-phenol resin compound member, the
dissipation factor D, which is related to the magnetic permeability
(refer to FIG. 2) and the dissipation factor D related to the
dielectric constant (refer to FIG. 3) increase in the GHz range and
this tendency is maintained throughout the high frequency range.
The relative magnetic permeability .mu. becomes reduced as the
dissipation factor D increases (refer to FIG. 2). It is also
observed that the relative dielectric constant .epsilon. also
becomes gradually reduced as the dissipation factor D increases
(refer to FIG. 3).
In the case of the NiZn ferrite, as shown in FIG. 4, the
dissipation factor D takes on a large value at approximately 1 GHz
and in the frequency range above 1 GHz, the value is almost 0. With
this, the relative magnetic permeability .mu., too, becomes
drastically reduced in the GHz range and approaches 1. Also, as
shown in FIG. 5, the relative dielectric coefficient .epsilon.
shows only a slight reduction tendency and the change in the
dissipation factor resulting from this is also very slight. This
means that when the insulating base is constituted with the NiZn
ferrite, there is an area in the GHz range where the filtering
characteristics are lost.
FIG. 6 shows the transmission characteristics observed when the
iron-phenol resin compound member (iron 60 vol %, particle diameter
2 mm the specimen in FIGS. 2 and 3) was used. As shown in the FIG.,
the attenuation in the transmission characteristics S21 becomes
pronounced at approximately 1 GHz and this attenuation continues up
to 20 GHz, which is the upper limit of the measurement. This means
that a low pass filter is constituted. As for the reflection
characteristics S11, attenuation of -10 dB is observed up to
approximately 10 GHz, indicating that the reflection is
sufficiently inhibited.
FIG. 7 shows the transmission characteristics observed when the
NiZn ferrite in the prior art was used. Although attenuation of the
transmission characteristics S21 is observed at approximately 1
GHz, the attenuation is reduced again at high frequencies exceeding
10 GHz, indicating that the low pass characteristics are not
obtained. FIG. 8 shows the transmission characteristics observed
when a compound member constituted of the NiZn ferrite-rubber resin
in the prior art was used. In this case, too, as in FIG. 7, the low
pass characteristics cannot be achieved.
Table 1 shows the entire evaluation results of the transmission
characteristics of various elements, specimens numbered 1 to 38,
which were prepared by using iron for the ferromagnetic metal
particles and also by changing the particle diameters and iron
content. In Table 1, the transmission characteristics S11 and S12
were evaluated by gains of the transmission characteristics S11 and
S21 in various cases with the frequency in the passing range at 100
MHz and the frequency in the stopping range at 5 GHz. Phenol, epoxy
and rubber resins were used for the insulating resin.
TABLE 1
__________________________________________________________________________
transmission reflection iron particle iron gain (S21) gain (S11)
size content dB dB No. .mu.m vol % 100 MHz 5 GHz 100 MHz 5 GHz
resin
__________________________________________________________________________
1 0.005 30 -0.3 -20 -20 -5 phenol*1 2 0.01 40 -0.2 -28 -25 -10
phenol 3 0.1 60 -0.2 -30 -25 -10 phenol 4 0.5 60 -0.2 -34 -25 -10
phenol 5 1 60 -0.2 -35 -24 -10 epoxy 6 2 60 -0.2 -37 -25 -11 epoxy
8 3 60 -0.2 -40 -25 -12 epoxy 9 5 60 -0.2 -40 -25 -12 epoxy 10 10
60 -0.2 -40 -25 -12 epoxy 11 30 60 -0.2 -40 -26 -11 epoxy 12 80 60
-0.2 -40 -26 -12 epoxy 13 100 60 -0.3 -35 -25 -10 epoxy 14 200 60
-1.3 -20 -15 -8 epoxy*2 15 1 10 -0.2 -10 -25 -8 epoxy 16 1 20 -0.2
-12 -25 -10 epoxy 17 1 30 -0.2 -20 -24 -11 epoxy 18 1 40 -0.2 -23
-25 -10 epoxy 19 1 50 -0.2 -30 -24 -11 epoxy 20 1 55 -0.2 -33 -26
-11 epoxy 21 1 63 -0.2 -45 -25 -12 epoxy 22 1 65 -0.2 -27 -23 -10
epoxy 23 1 70 -0.2 -25 -23 -10 epoxy 24 1 75 -0.2 -25 -23 -10 epoxy
25 1 80 -0.4 -25 -23 -8 epoxy 26 1 90 -1.2 -20 -25 -5 epoxy*1 27 10
10 -0.2 -10 -22 -9 phenol 28 10 20 -0.2 -12 -25 -9 phenol 29 10 30
-0.2 -15 -24 -10 rubber 30 10 40 -0.2 -25 -23 -10 rubber 31 10 50
-0.2 -30 -24 -10 rubber 32 10 55 -0.2 -40 -26 -10 rubber 33 10 63
-0.2 -40 -25 -10 phenol 34 10 65 -0.2 -27 -22 -10 phenol 35 10 70
-0.2 -27 -24 -9 epoxy 36 10 75 -0.4 -27 -25 -10 epoxy 37 10 80 -1.0
-27 -23 -8 epoxy 38 10 90 -1.5 -20 -21 -5 epoxy
__________________________________________________________________________
*1: irregular dispersion *2: occurence of roughness
The specimens numbered 2 to 13, 17 to 23 and 29 to 35, which
contain iron particles whose particle diameters range from 0.01
.mu.m to 100 .mu.m at content ratios of 30 vol % through 70 vol %,
showed transmission gains S21 of (-0.2 dB) to (-0.3 dB) with the
passing range frequency at 100 MHz and of (-15 dB) to (-45 dB) with
the stopping range frequency at 5 GHz, indicating that the
attenuation is small at 100 MHz frequency in the passing range and
that it is great at 5 GHz in the stopping range. Also, the
reflection gain S11 was within the range of (-22 dB) to (-26 dB) at
the passing range frequency of 100 MHz and of (-9 dB) to (-12 dB)
at the stopping range frequency at 5 GHz.
In comparison, the specimen number 1, which contained iron
particles whose diameter was 0.005 .mu.m, the specimen number 14,
which contained iron particles whose diameter was 200 .mu.m and the
specimens numbered 15, 16, 25 to 28 and 36 to 38 whose iron
particle contents were not within the range of 30 vol % through 75
vol % were demonstrated to be inferior in either transmission gain
S21 or reflection gain S11 at 1 MHz frequency in the passing range
and at 5 GHz in the stopping range. This leads to the conclusion
that it is desirable to use iron particles whose particle diameter
are within the range of 0.01 .mu.m to 100 .mu.m at iron content in
the range of 30 vol % to 75 vol %. Note that no significant
difference was observed in these characteristics that were
attributable to specific types of insulating resins employed.
Next, in reference to FIGS. 9 through 14, other embodiments of the
signal transmission element according to the present invention are
explained. In these FIGS., the same reference numbers are assigned
to components identical to those in FIG. 1 and their explanation is
omitted. In FIG. 9, the ground conductor 1 is provided continuously
over the entire surface of one side of the insulating magnetic body
3, with the two ends in the direction of its width extending around
to partially cover the surface on the other side so as to form gaps
between it and the signal conductor 2, which is formed on the other
surface of the insulating magnetic body 3. In FIG. 10, the ground
conductor 1 is provided over the entire surface of one side of the
insulating magnetic body 3 and the signal conductors 21 and 22 are
provided on either side surface of the insulating magnetic body 3
in the direction of its width.
In the signal transmission element shown in FIG. 11, ground
conductors 11 and 12 are provided on surfaces of the insulating
magnetic body 3 that face opposite each other and the signal
conductor 2 is embedded inside the insulating magnetic body 3 while
facing opposite the ground conductors 11 and 12. This particular
signal transmission element, therefore, is of the tri-plate type.
Although not shown, the signal transmission element according to
the present invention may take a structure which is provided with
other ground conductors provided on the remaining two surfaces of
the insulating magnetic body 3 for a total of 4 ground conductors,
one on each of the 4 surfaces. FIG. 12 shows the transmission
characteristics of the signal transmission element shown in FIG.
11. The line width W4 and the line thickness t of the signal
conductor 2 are selected at 1 mm and 30 .mu.m respectively. The
insulating magnetic body 3 is constituted with a iron-phenol resin
compound member (iron 50 vol %, particle diameter 2 .mu.m). The
dimensions of the signal transmission element are set at 4 mm in
width, W3, 3.5 mm in thickness, H3 and 3.2 mm in length, L3. As
shown in the FIG. 12, attenuation of the transmission
characteristics S21 becomes pronounced at approximately 1 GHz, and
this attenuation continues up to 20 GHz, which is the upper limit
in the measurement. This means that a low pass filter is
constituted. As for the reflection characteristics S11, attenuation
of -10 dB is observed up to approximately 10 GHz, indicating that
the reflection is sufficiently inhibited.
In the signal transmission element shown in FIG. 13, the ground
conductors 11 and 12 are provided opposite each other on opposite
surfaces of the insulating magnetic body 3 and the signal conductor
2 is embedded in the insulating magnetic body while facing opposite
the ground conductors 11 and 12. The signal conductor 2 is
constituted with a round copper wire. FIG. 14 shows the
transmission characteristics of the signal transmission element
shown in FIG. 13, in which the signal conductor 2 is constituted
with a copper wire, the diameter dl of which is set at 0.2 mm with
the insulating magnetic body 3 being constituted of an iron-phenol
resin compound member (iron 50 vol %, particle diameter 2 .mu.m).
The dimensions of which are set at 4 mm in width, W5, 3.5 mm in
thickness, H5 and 10 mm in length L5. As shown in FIG. 14,
attenuation of the transmission characteristics S21 becomes
pronounced at approximately 1 GHz, and this attenuation continues
up to 20 GHz, which is the upper limit in the measurement. This
means that a low pass filter is constituted. As for the reflection
characteristics S11, attenuation of approximately -10 dB is
observed up to approximately 10 GHz indicating that the reflection
is sufficiently inhibited.
FIG. 15 is a exploded perspective of yet another embodiment of the
signal transmission element according to the present invention,
FIG. 16 is a cross section of the signal transmission element shown
in FIG. 15 and FIG. 17 is a cross section through the line A17--A17
of the signal transmission element shown in FIG. 16. The ground
conductors 11 and 12 are provided on either of the external
surfaces of the insulating magnetic bodies 31 and 32. The signal
conductor 2 is embedded in the insulating magnetic body which is
formed with the insulating magnetic bodies 31 and 32. The signal
conductor 2 is structured as a meander line. On the outsides of the
ground conductors 11 and 12, insulating protective layers 33 and 34
respectively are laminated. These insulating protective layers 33
and 34 may be constituted of the same material as that constituting
the insulating magnetic bodies 31 and 32 or they may be constituted
of a different material. Both ends of the ground conductors 11 and
12 in the direction of their width are connected to either of the
ground terminal electrodes 110 and 120 which are attached to the
edges at both ends of the insulating magnetic bodies 31 and 32 and
the insulating protective layers 33 and 34 in the direction of
their width (or length). Both ends of the ground conductors 11 and
12 in the direction of their length (or width) are sealed off by
the insulating magnetic bodies 31 and 32. The signal conductor 2 is
connected to terminal electrodes 21 and 22 which are bonded to the
edges of both ends of the insulating magnetic bodies 31 and 32 and
the insulating protective layers 33 and 34 in the direction of
their length.
FIG. 18 shows the transmission characteristics of the signal
transmission element shown in FIGS. 15 to 17, in which the
insulating magnetic bodies 31 and 32 are constituted with a
carbonile iron-phenol resin compound member (iron 50 vol %,
particle diameter 2 .mu.m). As shown in FIG. 18, attenuation of the
transmission characteristics S21 becomes pronounced at
approximately 1 GHz, and this attenuation continues up to 20 GHz,
which is the upper limit in the measurement. This means that a low
pass filter is constituted. As for the reflection characteristics
S11, attenuation of approximately -10 dB is observed up to
approximately 10 GHz, indicating that reflection is sufficiently
inhibited.
It has already been mentioned that when constituting the insulating
magnetic body 3 in the electronic part according to the present
invention, ferromagnetic metal particles with diameters in the
range of 0.01 .mu.m to 100 .mu.m may be used. When selecting the
ideal particle size from the aforementioned particle size range,
one of the most desirable means is to determine the particle size
of the ferromagnetic metal particles based upon a skin depth which
will allow a high frequency magnetic field within the range of
operating frequencies to enter the inside of the particles. When
iron is selected for the ferromagnetic particles, the conductance
of iron is 1.07.times.10.sup.7 S/m and the magnetic permeability
produces the frequency characteristics shown in FIG. 19. The
frequency characteristics of the skin depth were calculated by
substituting values n the following formula to determine the skin
depth d of the metal particles;
with the frequency f, which can be obtained in FIG. 19, the
magnetic permeability .mu. of iron that corresponds to the
frequency f, and also the aforementioned conductance .sigma. of
iron (1.07.times.10.sup.7 S/m) and the results are shown in FIG.
20.
Since the high frequency magnetic field penetrates down to a depth
which is 3 times the skin depth, if the particle diameter of the
metal particles is several times that of the skin depth, the body
will provide sufficient high frequency magnetic dissipation. Since,
in this FIG. 20, the skin depth at 10 GHz is approximately 1 .mu.m,
the diameter of a particle whose radius is 3 times the skin depth,
is approximately 6 .mu.m. Accordingly, by constituting the
insulating magnetic body with metal particles with a particle
diameter of approximately 6 .mu.m or less, which are electrically
insulated from one another so that no electric current can run
among the particles, substantial high frequency magnetic
dissipation will be achieved over a wide frequency range.
Fine particles of pure iron (carbonile iron particles) with the
particle diameter of several .mu.m or less, which are obtained by
thermally decomposing carbonile iron would be a desirable example
of such fine ferromagnetic metal particles. When these iron
particles are hardened with an insulator, a body is obtained that
demonstrates a high degree of dissipation over millimeter
waves.
FIG. 21 is a perspective of yet another embodiment of the signal
transmission element according to the present invention with the
signal conductor included in the element exaggerated. FIG. 22 is an
external perspective view of the signal transmission element shown
in FIG. 21. FIG. 23 is a cross section of the signal transmission
element shown in FIGS. 21 and 22 and FIG. 24 is a diagram of an
equivalent circuit of the signal transmission element according to
the present invention shown in FIGS. 21 to 23. The signal
transmission element in these FIGS. includes at least one ground
conductor 1, at least one signal conductor 2 and an insulating
magnetic body 3. The ground conductor 1 is formed on a surface of
the insulating magnetic body 3 and the signal conductor 2 is
embedded in the insulating magnetic body 3.
The signal conductor 2 is formed spirally. This spiral signal
conductor is coiled around another insulating magnetic body 4
distinct from the insulating magnetic body 3. The signal conductor
2 is coiled in such a manner that the turning angle is the same for
each turn and the coil advances over intervals in the direction of
the coil axis. The intervals between the turns should be longer
than the diameter of the wire that constitutes the signal conductor
2.
The two ends of the signal conductor 2 are separately connected to
a pair of.-terminal electrodes 51 and 52 which are attached to the
opposite two ends of the insulating magnetic body 3. The ground
conductor 1 is formed on a surface of the insulating magnetic body
3 between the pair of terminal electrodes 51 and 52 in the state in
which it is electrically insulated from the terminal electrodes 51
and 52. Reference numbers 61 and 62 indicate the insulating areas.
The insulation areas 61 and 62 are formed in a ring shape.
The signal transmission element shown in FIGS. 21 to 23 according
to the present invention is a 3-terminal type equivalent circuit in
which, as shown in FIG. 24, the line inductance generated by the
signal conductor 2 is inserted between the terminal electrodes 51
and 52, and the ground conductor 1 is T-linked to the line
inductance.
Since the magnetic dissipation of the signal transmission element
expressed by the circuit in FIG. 24 is in proportion to the line
inductance L, the dissipation is large in the frequency band in
which the line impedance L is equal to or greater than the
impedance output from the drive circuit (not shown), demonstrating
equivalent characteristics to those of a low pass filter. However,
unlike a low pass filter constituted with an ordinary low
dissipation circuit element, the energy of the signal is absorbed
in the element and is not reflected in the attenuation band. By
inserting the signal conductor 2 inside the magnetic body 3 which
is formed by insulating metal particles with small particle
diameters, a signal transmission element that demonstrates large
magnetic dissipation over a wide frequency range and that, at the
same time, absorbs undesired frequency components, is achieved.
The signal transmission element according to the present invention
is well suited to constitute a transmission line with a large
dissipation and the attenuation factor is determined by the ratio
against the output impedance from the drive circuit. With the
frequency at which the dissipation increases defined as the cutoff
frequency, as in the case of an ordinary filter, the cutoff
frequency goes down in approximate proportion to the length of the
line. Consequently, a structure which accommodates an electrically
long line within a limited volumetric space is essential for
achieving miniaturization while securing a high cutoff
frequency.
In the case of the embodiment shown in FIGS. 21 to 23, as has been
mentioned earlier, the signal conductor 2 is formed spirally and is
coiled in such a manner that the coil advances over approximately
equal intervals in the direction of the coil axis. In other words,
each turn goes around in the same direction. Since this structure
ensures that the magnetic fluxes generated at each turn do not
cancel one another out overall, it becomes possible to form an
electrically long line within a limited volumetric space and to
obtain a large inductance, thereby achieving a high attenuation
factor.
Next, the insulating magnetic body 3 containing carbonile iron
shows little dissipation at 1 GHz or lower, as is obvious from the
dissipation frequency characteristics of carbonile iron. Therefore,
when constituting an absorption type filter for this frequency
band, a problem may arise of insufficient dissipation
characteristics. As the means for solving this problem, in this
embodiment, the spiral signal conductor 2 is coiled on the
insulating magnetic body 4, as explained earlier. The insulating
magnetic body 4 is constituted of an insulating magnetic material
with great dissipation at 1 GHz or lower, typically a ferrite
magnetic body. This structure achieves an absorption type filter
which retains sufficient dissipation characteristics even in the
frequency band of 1 GHz or lower.
To be more specific, the wiring material for the signal conductor 2
has a cross section diameter of 0.1 mm and is coiled 8 times around
the insulating magnetic body 4 which is constituted of a ferrite
dowel with a diameter of 1.2 mm. Its periphery is hardened with an
insulating magnetic body 3, mainly constituted of carbonile iron
particles, to a thickness of approximately 0.3 mm, to form a
rectangular parallelopiped body. After forming a film over the
entirety of the outside of the rectangular parallelopiped body by
electroless plating, little grooves are cut into the plate film to
form insulating gaps 61, 62 in such a manner that areas 51, 52 to
function as terminal conductors are left on both sides. By doing
so, a signal transmission element with a 3-terminal structure
(refer to FIGS. 21 to 23), provided with the ground conductor 1 in
the middle and the terminal conductors 51 and 52 on either side of
the ground conductor 1, which are insulated by the insulating gaps
61 and 62, is achieved. The terminal conductors 51 and 52 at both
ends which are separated by the insulating gaps, are then
electrically connected with the signal conductor 2 on the inside.
In this manufacturing process, production is performed at a
temperature of 300 or less, which means that the thermal treatment
at temperatures of 1000 or higher that is required for
manufacturing ceramic elements in the prior art, is not necessary.
Thus, the energy required for production is greatly reduced.
FIG. 25 shows the transmission characteristics of the signal
transmission element according to the present invention and FIG. 26
shows its reflection characteristics. The transmission
characteristics shown in FIG. 25 indicate that the cutoff frequency
of this element, i.e., the frequency at which the attenuation is -3
dB, is approximately 165 GHz and that in the frequency range higher
than the cutoff frequency, the attenuation increases as the
frequency becomes higher. In the range of 4 GHz to 20 GHz,
attenuation of approximately -20 dB is maintained practically
constant. Also, as shown in FIG. 26, the reflection characteristics
at 1 GHz or higher are -10 dB or less and are also very stable.
Next, FIG. 27 shows the reflection characteristics for shorting and
opening the signal transmission element according to the present
invention. In the case of either shorting or opening, the
reflection characteristics at 1 GHz or higher do not change much.
This indicates that most of the energy sent into the element is
absorbed inside the element when the frequency is at 1 GHz or
higher. This further means that the reflection characteristics are
determined by the ratio of the input impedance of the element and
the impedance on the drive side and that it does not depend on the
impedances within the element or on the load side.
If the signal transmission element shown in FIGS. 21 to 24 is to be
regarded as a TEM transmission line comprising a transmission line
constituted of the signal conductor 2 and a ground conductive
member constituted of the ground conductor 1, its structure can be
illustrated in a development along the transmission line as shown
in FIG. 28. According to transmission line theory, the
characteristic impedance Zo of this line can be expressed with the
following formula (2)
By substituting values for the various factors constituting the
line described earlier, i.e., the line diameter d=0.1 mm, the line
interval r=0.3 mm, the relative dielectric constant .epsilon..sub.r
=90 and the relative magnetic permeability .mu..sub.r =9 in the
equation (2) above, the characteristic impedance Zo is calculated
to be 36.5.OMEGA.. The reflection coefficient .GAMMA. when this
signal transmission element is driven with the drive side impedance
at 50.OMEGA., is calculated thus; ##EQU1##
Although there is a significant difference when this reflection
coefficient is compared to the reflection coefficient calculated
using the actual measured values in the reflection dissipation,
this difference can be assumed to be caused by a reflection which
occurs mainly due to the structure of the input/output terminal,
which does not constitute the transmission line.
The results of the tests show that when the coil is wound 4 times,
the cutoff frequency increases to 330 MHz. This means that the
cutoff frequency can be arbitrarily selected with the number of
times the coil is wound. As explained earlier, the characteristic
impedance can be determined by selecting appropriate values for the
line diameter d, the line interval r, the relative dielectric
constant .epsilon..sub.r and the relative magnetic permeability
.mu..sub.r. Since the drive impedance is not always set at
50.OMEGA. in an actual circuit and may sometimes exceed 100.OMEGA.,
it is a great advantage that in this signal transmission element,
simply by selecting suitable values for the various factors
constituting the line, impedances over a wide range of frequencies
can be determined.
For the signal transmission element shown in FIGS. 21 to 23, the
cutoff frequency and the characteristic impedance can also be
indicated by pouring paint into the insulating gaps 61, 62 which
are formed as grooves by a cutting process.
In the signal transmission element shown in FIGS. 21 to 23, since
at least one ground conductor 1 and at least one signal conductor 2
are provided at the insulating magnetic body 3, a signal
transmission element which performs signal transmission can be
obtained in an application to a signal transmission passage by
grounding the ground conductor 1 and inserting the signal conductor
2 into the signal transmission passage.
Since the insulating magnetic body 3 is constituted of a compound
member in which ferromagnetic metal particles are mixed in an
insulating resin, the undesired high frequency components in the
high frequency range which are included in a signal passing through
the signal conductor can be reliably absorbed through the absorbing
effect of the insulating magnetic body 1. To be more specific, a
signal transmission element which has the absorbing effect in the
high frequency band of 1 GHz or higher (high frequency stopping)
and which passes signals that belong in the lower frequency bands
(low pass), is achieved. Also, the impedance can be maintained
almost constant up to a frequency of approximately 20 GHz and
reflection can be kept at approximately -10 dB. This means that the
signal transmission element according to the present invention is
suited to be used as a low pass filter.
In the signal transmission element in this embodiment, too, the
ferromagnetic metal is used in the form of particles with their
particle size in the range of 0.01 .mu.m to 100 .mu.m in diameter.
As mentioned earlier, when selecting the ideal particle size from
the aforementioned particle size range, one of the most desirable
means that should be applied is to determine the particle size of
the ferromagnetic metal particles based upon a skin thickness which
allows high frequency magnetic fields within the range of operating
frequencies to enter the inside of the particles. By doing so, the
high frequency magnetic field can be ensured to penetrate fully and
effectively into the ferromagnetic metal particles. As a result,
the magnetic dissipation characteristics of the ferromagnetic metal
particles present in the insulating magnetic body contribute to
generating, greatly improving the efficiency of their use.
Furthermore, the insulating magnetic body 3 that absorbs the high
frequency components is constituted of a compound member which
combines ferromagnetic metal particles and an insulating resin with
a ground conductor 1 and the signal conductor 2 both provided at
the insulating magnetic body 3, achieving a very simple
structure.
The mechanism of low frequency passing and high frequency stopping
in the signal transmission element according to the present
invention is almost identical to that of the signal transmission
element that was explained in reference to FIGS. 1 to 14 earlier
and its detailed explanation is omitted here.
Also, as has been explained, the structure of the signal
transmission element according to the present invention is simple
compared with that of band filters in the prior art and also the
cost of basic materials is lower. In addition, it does not require
processes such as firing that are energy costly. Thus, a great
reduction in production cost is achieved.
There are a variety of possibilities for the structure in which a
spiral signal conductor 2 is embedded inside an insulating magnetic
body 3 to constitute a TEM line with a ground conductor 1 provided
on the outside. For instance, as shown in FIGS. 29 and 30, the
spirally formed signal conductor 2 may be embedded in such a manner
that the direction of its winding is at a right angle to the
direction of the terminal conductors 51 and 52. The same reference
numbers are assigned to components in FIGS. 29 and 30 that are
identical to those in FIGS. 21 to 23 and their detailed explanation
is omitted.
[EXAMPLES OF APPLICATION]
As examples of application of the signal transmission element
according to the present invention as an absorption type low pass
filter, an instance of outside band characteristics improvement in
a band pass filter and also an instance of undesired signal removal
in an intermediate frequency amplifying circuit are explained in
reference to FIGS. 31 and 32.
(a) Application example in which outside band characteristics are
improved in a band pass filter
The FIG. shows an example of an application in which the signal
transmission element according to the present invention is used to
improve the outside band characteristics of a band pass filter
inserted in a high frequency power amplifying circuit such as a
cellular phone. The signal transmission element according to the
present invention is inserted as the filter 9 located behind the
band pass filter 8 and in front of the duplexer 10. In FIG. 31,
reference numbers 11 and 12 indicate a reception circuit and an
antenna respectively.
The band pass filter 8, which is inserted in a high frequency power
amplifying circuit such a cellular phone, is required to have a
stopping function at frequencies that are odd-number multiples of
the carrier frequency in order to stop higher harmonics generated
due to distortion caused at the power amplifier 7 as well as to
provide frequency selectability in the vicinity of the passing
band. In a frequency range such as this, the circuit elements of
the band pass filter 8 are distributed constant circuit elements
and very often, they are very different from the stopping function
performance in the vicinity of the carrier frequency. Consequently,
in order to improve the characteristics outside the band, the
stopping performance is changed sometimes to such an extend that
the characteristics inside the band are affected.
In order to avoid such a problem, inserting a low pass filter which
operates in the relevant frequency band may be considered, but this
would increase the production costs. Alternatively, by inserting
the signal transmission element according to the present invention,
which has absorption characteristics in the relevant frequency
band, at the position indicated in FIG. 31 as the filter 9, the
problem described above can be eliminated with its absorbing effect
in the higher harmonics range, without much affecting the signal at
the carrier frequency. Compared with a low pass filter, the signal
transmission element according to the present invention is much
less costly and will not increase production costs significantly.
Furthermore, as the undesired higher harmonics are effectively
absorbed, circuit stabilization is achieved.
(b) Application example in which undesired signals are removed in
an intermediate frequency amplifying circuit
FIG. 32 shows an application example in which a signal transmission
element according to the present invention is used as a filter for
removing undesired signals in an intermediate frequency amplifying
circuit. The signal transmission element according to the present
invention is used as a filter 15 for the removal of undesired
signals in an intermediate frequency amplifying circuit. Reference
number 14 indicates a local oscillator.
A signal that has leaked from the high frequency amplifying circuit
sometimes returns to be superimposed on the signal line extending
from the high frequency mixer circuit 13 through the intermediate
frequency amplifying circuit 16. In order to avoid problems in the
intermediate frequency amplifying circuit 16 caused by such a
signal, the signal transmission element according to the present
invention is inserted as shown in FIG. 32 as the filter 15, whose
cutoff frequency is set somewhere between the carrier frequency
supplied from the local oscillator 14 and the intermediate
frequency. With this, the undesired signal is absorbed inside the
filter 15 constituted of the signal transmission element according
to the present invention, which contributes to stabilization of the
circuit operation.
Next, an embodiment in which the electronic part according to the
present invention is employed as a connector is explained as a
specific example.
FIG. 33 is a side elevation of the connector according to the
present invention and FIG. 34 is a cross section through line
A34--A34. The connector according to the invention includes, at
least, a pair of conductors; a ground conductor 1 and a signal
conductor 2, and an insulating magnetic body 3. The signal
conductor 2 is provided in such a manner that it penetrates the
insulating magnetic body 3. The ground conductor 1 is mounted on
the insulating magnetic body 3 and is electrically insulated from
the signal conductor 2 by the insulating magnetic body 3. As a
result, a connector with a simple structure, in which the ground
conductor 1 is grounded and the terminal conductor 2 is insulated
from the ground conductor 1 by the insulating magnetic body 3, is
achieved. The ground conductor 1 shown in the FIGS., is shaped
cylindrically with its two ends forming threaded portions 101 and
102, and it is grounded via a cable or a circuit system which is
connected to the threaded portions 101 and 102. The signal
conductor 2 is cylindrical, with a slit 21 provided running from
both ends toward the center and it has a tensile property. A
pin-type connector may be connected to the signal conductor 2.
As explained earlier, the insulating magnetic body 3 is constituted
of a compound material in which ferromagnetic metal particles and
an insulating resin are mixed. The ferromagnetic metal particles
are preferably iron, in particular, carbonyl iron, of which various
particle diameters can be selected within a range of 0.01 .mu.m to
100 .mu.m. The insulating resin to be mixed with the ferromagnetic
metal particles should be constituted of one type or several
different types of the following: phenol epoxy, rubber or Teflon.
Also, as explained earlier, when selecting the ideal particle size
from the aforementioned particle size range one of the most
desirable means that should be applied is to determine the particle
size of the ferromagnetic metal particles based upon the skin depth
which allows high frequency magnetic fields within the range of
operating frequencies to enter the inside of the particles.
Now, the method for producing the connector according to the
present invention and the characteristics of the specimens thus
obtained are described. First, ferromagnetic metal particles and
insulating resin were mixed and a specimen of the insulating
magnetic body for an SMA 3.5 mm connector was formed by pressing.
Then, an insulating magnetic body 3 was obtained by hardening the
insulating resin with an appropriate thermal treatment on the
specimen. The insulating magnetic body 3 was then impregnated with
the resin and was dried and hardened.
Next, the insulating magnetic body 3 was inserted in a ground
conductor 1, which was then followed by insertion of a signal
conductor 2 into the insulating magnetic body 3 to constitute an
SMA 3.5 mm connector. At this point, the thickness of the signal
conductor 2 should be adjusted so that the characteristic impedance
is set to 50.OMEGA., For instance, when the length L1 of the
insulating magnetic body 3 is 10 mm, the diameter .PHI.1 of the
signal conductor 2 should be within the range of 0.1 to 1.0 mm.
The characteristics of the connector described above were evaluated
for the complex magnetic permeability and the complex dielectric
constant of the compound material constituting the insulating
magnetic body 3 and the transmission characteristics S11 and S21 of
the connector. Since the method of evaluation employed here is
identical to that used in evaluating the signal transmission
element in FIG. 1, its detailed explanation is omitted. Also, the
ferromagnetic metal particles used for this connector were
identical to those used for the signal transmission element shown
in FIG. 1, exhibiting complex magnetic permeability characteristics
for the iron-phenol resin compound material identical to those
shown in FIG. 2 and complex dielectric characteristics for the
iron-phenol resin compound material identical to those shown in
FIG. 3. Therefore, descriptions of these characteristics are
omitted here.
Furthermore, since the transmission characteristics in discussion
here, too, are identical to transmission characteristics S11 and
S21 shown in FIG. 6 when the iron-phenol resin compound material
was used, a detailed explanation of that is also omitted. As
explained earlier, in reference to FIG. 6, in the connector in this
embodiment, attenuation of the transmission characteristics S21
becomes pronounced at approximately 1 GHz, and this attenuation
continues up to 20 GHz, which is the upper limit in the
measurement. This means that high frequency noise is absorbed. As
for the reflection characteristics S11, attenuation of -10 dB is
observed up to approximately 10 GHz, indicating that reflection is
sufficiently inhibited.
Table 2 shows the overall results of the evaluation of the
transmission characteristics of the various connectors specimens
numbered 1/T2 to 38/T2 which were prepared by using iron for the
ferromagnetic metal particles and also by changing the particle
diameter and the iron content. The transmission characteristics S11
and S12 were evaluated according to gain in the transmission
characteristics S11 and S21 in various cases with the frequency in
the passing range at 100 MHz and the frequency in the stopping
range at 5 GHz. Phenol, acrylic, Teflon and epoxy resins were used
for the insulating resin as appropriate.
TABLE 2
__________________________________________________________________________
transmission reflection iron particle iron gain (S21) gain (S11)
insulation size content dB dB resitance No. .mu.m vol % 100 MHz 5
GHz 100 MHz 5 GHz .OMEGA. resin
__________________________________________________________________________
1/T2 0.005 30 -0.3 -20 -20 -5 >10.sup.11 phenol*1 2/T2 0.01 40
-0.2 -28 -25 -11 >10.sup.11 phenoi 3/T2 0.1 60 -0.2 -30 -25 -12
>10.sup.11 phenol 4/T2 0.5 60 -0.2 -34 -25 -12 >10.sup.11
phenol 5/T2 1 60 -0.2 -39 -26 -12 >10.sup.11 epoxy 6/T2 2 60
-0.2 -39 -26 -12 >10.sup.11 epoxy 8/T2 3 60 -0.2 -41 -24 -12
>10.sup.11 epoxy 9/T2 5 60 -0.2 -41 -25 -12 >10.sup.11 epoxy
10/T2 10 60 -0.2 -43 -25 -12 >10.sup.11 epoxy 11/T2 30 60 -0.2
-43 -26 -11 10.sup.10 epoxy 12/T2 50 60 -0.2 -43 -26 -12 10.sup.10
epoxy 13/T2 100 60 -0.3 -35 -25 -10 10.sup.9 epoxy 14/T2 200 60
-1.3 -20 -15 -8 10.sup.9 epoxy*2 15/T2 1 10 -0.2 -10 -25 -8
>10.sup.11 epoxy 16/T2 1 20 -0.2 -12 -25 -11 >10.sup.11 epoxy
17/T2 1 30 -0.2 -30 -24 -12 >10.sup.11 epoxy 18/T2 1 40 -0.2 -34
-25 -12 >10.sup.11 epoxy 19/T2 1 50 -0.2 -40 -24 -12
>10.sup.11 epoxy 20/T2 1 55 -0.2 -43 -26 -11 >10.sup.11 epoxy
21/T2 1 63 -0.2 -45 -25 -12 >10.sup.11 epoxy 22/T2 1 65 -0.2 -40
-23 -10 10.sup.10 epoxy 23/T2 1 70 -0.2 -35 -23 -10 10.sup.10 epoxy
24/T2 1 75 -0.2 -25 -23 -10 10.sup.9 epoxy 25/T2 1 80 -0.4 -25 -23
-8 10.sup.9 epoxy 26/T2 1 90 -1.2 -20 -25 -5 10.sup.9 epoxy*1 27/T2
10 10 -0.2 -10 -22 -9 10.sup.11 phenol 28/T2 10 20 -0.2 -12 -25 -9
10.sup.11 phenol 29/T2 10 30 -0.2 -30 -24 -10 10.sup.11 rubber
30/T2 10 40 -0.2 -35 -24 -10 10.sup.11 rubber 31/T2 10 50 -0.2 -38
-25 -10 10.sup.11 rubber 32/T2 10 55 -0.2 -40 -26 -10 10.sup.11
rubber 33/T2 10 63 -0.2 -40 -25 -10 10.sup.11 phenol 34/T2 10 65
-0.2 -37 -22 -10 10.sup.10 phenol 35/T2 10 70 -0.2 -37 -24 -9
10.sup.10 epoxy 36/T2 10 75 -0.4 -27 -25 -10 10.sup.9 epoxy 37/T2
10 80 -1.0 -27 -23 -8 10.sup.9 epoxy 38/T2 10 90 -1.5 -20 -21 -5
10.sup.9 epoxy*1
__________________________________________________________________________
*1: irregular dispersion *2: occurence of roughness
The specimens numbered 2/T2 to 13/T2, 17/T2 to 23/T2 and 29/T2 to
35/T2 which contain iron particles whose diameters are within the
range of 0.01 .mu.m to 100 .mu.m at a content range of 30 vol % to
70 vol % show a transmission gain S21 of (-0.1 dB) or (-0.3 dB) at
the passing band frequency of 100 MHz, and show a transmission gain
S21 of (-28 dB) to (-60 dB) at the stopping band frequency of 5
GHz. This means that attenuation is small at the passing band
frequency of 100 MHz and is large at the stopping band frequency of
5 GHz. The reflection gain S11 is within the range of (-23 dB) to
(-27 dB) at the passing band frequency of 100 MHz and is within the
range of (-9 db) to (-12 dB) at the stopping band frequency of 5
GHz.
In comparison, the specimen numbered 1/T2, which contains iron
particles whose diameter is 0.005 .mu.m, the specimen numbered
14/T2, which contains iron particles whose diameter is 200 .mu.m
and the specimens numbered 15/T2, 16/T2, 24/T2 to 28/T2 and 36/T2
to 38/T2 whose iron particle contents are not within the range of
30 vol % through 70 vol %, are shown to be inferior in either the
transmission gain S21 or in the reflection gain S11 at 100 MHz
frequency in the passing range and at 5 GHz frequency in the
stopping range.
This leads to the conclusion that it is desirable to use iron
particles whose particle diameters are within the range of 0.01
.mu.m to 100 .mu.m at an iron content in the range of 30 vol % to
70 vol %. In particular, the specimens numbered 3/T2 to 10/T2,
19/T2 to 21/T2 and 31/T2 to 33/T2 which contain iron particles
whose diameters are within the range of 0.1 .mu.m to 10 .mu.m at a
content range of 50 vol % to 63 vol % show a transmission gain S21
of (-0.1 dB) at the passing band frequency of 100 MHz, and show a
transmission gain S21 of (-54 dB) to (-60 dB) at the stopping band
frequency of 5 GHz. This means that attenuation is small at the
passing band frequency of 100 MHz and is large at the stopping band
frequency of 5 GHz. The reflection gain S11 is within the range of
(-24 dB) to (-26 dB) at the passing band frequency of 100 MHz and
is within the range of (-10 dB) to (-12 dB) at the stopping band
frequency of 5 GHz, demonstrating that a connector with stable
filter characteristics, superior low pass characteristics and high
frequency stopping is achieved. Therefore, the more desirable range
of particle diameters for the ferromagnetic metal particles is 0.1
.mu.m to 10 .mu.m and the more desirable content range for the
ferromagnetic metal particles is 50 vol % to 63 vol %. Note that no
significant difference in the characteristics attributable to
specific types of insulating resins employed is evident.
The present invention may be applied to connectors with different
structures such as a connector provided with a plurality of
terminal conductors. As specific examples to which the present
invention can be applied, multiple pin type connectors in the prior
art disclosed in Japanese Examined Patent Publication No. 3108/1986
and Japanese Examined Patent Publication No. 49661/1990 can be
cited. By constituting the noise filter element or the insulating
housing used in those multiple pin connectors in the known art with
the insulating magnetic body disclosed in the present invention,
multiple pin connectors with high frequency stopping and low pass
characteristics can be obtained to ensure that the high frequency
components in the high frequency range are reliably absorbed.
Next, as a specific example of application, an embodiment in which
the electronic part according to the present invention is employed
as a circuit board is explained in reference to FIG. 35. The
circuit board according to the present invention includes, at
least, two conductors 1 and 2 and an insulating magnetic body 3.
The conductors 1 and 2 are provided on the opposite sides of the
insulating magnetic body 3 so as to sandwich the insulating
magnetic body 3. Consequently, the conductor 1 may be used, for
instance, as a ground conductor and the conductor 2 may be used as
a signal conductor. In an actual operating situation, the conductor
2 is patterned to serve as the signal conductor to be used in a
circuit board. For the conductors 1 and 2, known materials from the
prior art is used as the material for conductor pattern formation
in circuit boards, typically, a material whose main component is
copper.
As explained earlier, the insulating magnetic body 3 is constituted
of a compound material in which ferromagnetic metal particles and
an insulating resin are mixed. The ferromagnetic metal particles
should be, preferably, iron and in particular, carbonile iron.
Various different particle diameters can be selected within a range
of 0.01 .mu.m to 100 .mu.m, using either iron or carbonyl iron, and
the insulating resin to be mixed with the ferromagnetic metal
particles may be constituted of one type or several different types
of the following: phenol, epoxy, rubber and Teflon. Also, as
explained earlier, when selecting the ideal particle size from the
aforementioned particle size range, one of the most desirable means
that should be applied is to determine the particle size of the
ferromagnetic metal particles based upon the skin depth which
allows high frequency magnetic fields within the range of operating
frequencies to enter the inside of the particles. However, note
that when constituting a circuit board, from the viewpoint of
reinforcing mechanical strength, it is preferable to add fiber such
as in fiberglass to the material that has, as its main component,
the insulating resin described above.
FIG. 36 is a side elevation of another embodiment of the circuit
board according to the present invention. In this embodiment, the
conductors 1 and 2 are provided on the opposite sides of the
insulating magnetic body 3 so as to sandwich it, an other
insulating magnetic body 300 is provided on top of the conductor 1
and a conductive layer 100 is provided on the insulating magnetic
body 300, to constitute a circuit board with a multilayer
structure. Although it is desirable to constitute the insulating
magnetic body 300 with the compound material described earlier, it
may also be constituted with another insulating material of the
known art.
Now, the method for manufacturing the circuit board according to
the present invention and the characteristics of the specimens thus
obtained are explained. First, ferromagnetic metal particles and an
insulating resin are dissolved in a solvent. The viscosity of this
solution should be adjusted to a suitable value. The solution thus
obtained is then soaked in a glass fiber and then it is dried to
produce a thin sheet. Several tens of such sheets are then
laminated together and on both surfaces of the resulting laminated
body, copper foil is laminated. Then, a heat pressing treatment is
performed on this laminated body. As the insulating resin becomes
thermally hardened, the entire body is hardened. After this, a
laminated copper-coated board 100 mm long, L1, 100 mm wide, W1 and
10.635 m thick, H is obtained.
Then, the copper foil coatings on the two opposite surfaces of the
insulating magnetic body 3 are patterned as shown in FIG. 37 by
going through such processes as photo etching, to form the ground
conductor 1 and the signal conductor 2. The line width W2 and the
line length L2 of the signal conductor 2 are determined so that the
characteristic impedance of 50.OMEGA. is achieved in the low
frequency range. In the embodiment, by taking into consideration
the relative magnetic permeability and the relative dielectric
constant of the compound material, a linear pattern with the line
width W2, of 0.5 mm to 1.0 mm and a line length L2, of 10 mm was
provided. The signal conductor 2 was formed by etching the copper
foil. Alternatively, the ground conductor 1 and the signal
conductor 2 may be formed through vacuum deposition.
In order to evaluate the characteristics of the circuit board
described above, the transmission characteristics S11 and S21 of
the compound material constituting the insulating magnetic body 3
were used. NiZn ferrite which is usually used for filters is used
as a reference material. The characteristics of the connector
described above were evaluated on the complex magnetic permeability
and the complex dielectric constant of the compound material
constituting the insulating magnetic body 3 and the transmission
characteristics S11 and S21 of the connector. Since the method of
evaluation employed here is identical to that used in evaluating
the signal transmission element in FIG. 1, its detailed explanation
is omitted. Also, the ferromagnetic metal particles used were
identical to those used for the signal transmission element shown
in FIG. 1 exhibiting complex magnetic permeability characteristics
of the iron-phenol resin compound material identical to those in
FIG. 2 and exhibiting complex dielectric characteristics of the
iron-phenol resin compound material identical to those in FIG. 3.
Therefore, their detailed descriptions are omitted here.
FIG. 38 shows the transmission characteristics achieved in the
embodiment described above. As shown in the FIG., in this
embodiment, too, attenuation of the transmission characteristics
S21 becomes pronounced at approximately 1 GHz, and this attenuation
continues up to 20 GHz, which is the upper limit in the
measurement. This means that the high frequency noise is absorbed.
As for the reflection characteristics S11, attenuation of -10 dB is
observed up to approximately 10 GHz, indicating that the reflection
is sufficiently inhibited. Table 3 shows the overall results of the
evaluation of the transmission characteristics of the various
specimens numbered 1/T3 to 38/T3 which were prepared by using iron
for the ferromagnetic metal particles and also by changing the
particle diameter and iron content. The transmission
characteristics S11 and S21 were evaluated by gains of the
transmission characteristics S11 and S21 in various cases with the
frequency in the passing range at 100 MHz and the frequency in the
stopping range at 5 GHz. Phenol, epoxy and rubber resins were used
for the insulating resin as appropriate.
TABLE 3
__________________________________________________________________________
iron particle iron transmission reflection size content gain (S21)
gain (S11) No. .mu.m vol % 100 MHz 5GHz 100 MHz 5 GHz resin note
__________________________________________________________________________
1/T3 0.005 30 -0.2 -40 -20 -5 acrylic *1 2/T3 0.01 40 -0.1 -52 -24
-11 acrylic 3/T3 0.1 60 -0.1 -55 -25 -12 acrylic 4/T3 0.5 60 -0.1
-55 -25 -11 acrylic 5/T3 1 60 -0.1 -55 -24 -12 acrylic 6/T3 2 60
-0.1 -54 -25 -11 teflon 8/T3 3 60 -0.1 -60 -25 -12 teflon 9/T3 5 60
-0.1 -60 -25 -12 teflon 10/T3 10 60 -0.1 -60 -25 -12 phenol 11/T3
30 60 -0.1 -60 -26 -12 phenol 12/T3 80 60 -0.1 -60 -26 -12 phenol
13/T3 100 60 -0.2 -55 -25 -11 phenol 14/T3 200 60 -1.0 -40 -15 -9
phenol *2 15/T3 1 10 -0.1 -20 -25 -9 epoxy 16/T3 1 20 -0.1 -22 -25
-11 epoxy 17/T3 1 30 -0.1 -40 -24 -12 epoxy 18/T3 1 40 -0.1 -43 -25
-10 epoxy 19/T3 1 50 -0.1 -55 -24 -11 epoxy 20/T3 1 55 -0.1 -55 -26
-11 epoxy 21/T3 1 63 -0.1 -60 -25 -12 epoxy 22/T3 1 65 -0.1 -55 -23
-11 epoxy 23/T3 1 70 -0.1 -50 -23 -12 phenol 24/T3 1 75 -0.1 -48
-23 -10 phenol 25/T3 1 80 -0.2 -45 -23 -9 phenol 26/T3 1 90 -1.0
-40 -24 -3 phenol *1 27/T3 10 10 -0.1 -20 -23 -9 phenol 28/T3 10 20
-0.1 -24 -24 -9 phenol 29/T3 10 30 -0.1 -30 -24 -10 phenol 30/T3 10
40 -0.1 -50 -24 -11 phenol 31/T3 10 50 -0.1 -55 -25 -10 acrylic
32/T3 10 55 -0.1 -60 -26 -10 acrylic 33/T3 10 63 -0.1 -60 -25 -12
acrylic 34/T3 10 65 -0.1 -50 -24 -10 acrylic 35/T3 10 70 -0.1 -50
-27 -9 acrylic 36/T3 10 75 -0.1 -50 -25 -10 acrylic 37/T3 10 80
-0.8 -45 -24 -8 acrylic 38/T3 10 90 -1.5 -40 -22 -5 acrylic
__________________________________________________________________________
*1: irregular dispersion *2: occurenoe of roughness
The specimens numbered 2/T3 to 13/T3, 17/T3 to 23/T3 and 29/T3 to
35/T3 which contain iron particles whose diameters were within the
range of 0.01 .mu.m to 100 .mu.m, at a content range of 30 vol % to
70 vol % showed transmission gains S21 of (-0.2 dB) to (-0.3 dB) at
the passing band frequency of 100 MHz, and showed transmission
gains of (-28 dB) to (-60 dB) at the stopping band frequency of 5
GHz. This means that attenuation is small at the passing band
frequency of 100 MHz and is large at the stopping band frequency of
5 GHz. The reflection gain S11 was within the range of (-22 dB) to
(-27 dB) at the passing band frequency of 100 MHz and was within
the range of (-9 db) to (-12 dB) at the stopping band frequency of
5 GHz. An insulating resistance of 109 or over was achieved,
presenting no problems in insulation.
In comparison, the specimen numbered 1/T3, which contained iron
particles whose diameter was 0.005 .mu.m, the specimen numbered
14/T3, which contained iron particles whose diameter was 200 .mu.m
and the specimens numbered 15/T3, 16/T3, 24/T3 to 28/T3 and 36/T3
to 38/T3 whose iron particle contents were not within the range of
30 vol % through 70 vol % were shown either to be inferior in
transmission gain S21 or reflection gain S11 at 100 MHz frequency
in the passing range and 5 GHz of the frequency in the stopping
range. Therefore, the desirable range for particle diameter of the
ferromagnetic metal particles is 0.01 .mu.m to 100 .mu.m and the
desirable content range of the ferromagnetic metal particles is 30
vol % to 70 vol %. Note that no significant difference in the
characteristics attributable to specific types of insulating resins
employed was evident.
While the invention has been particularly shown and described with
reference to preferred embodiments thereof, it will be understood
by those skilled in the art that various changes in form and detail
may be made therein without departing from the spirit, scope and
teaching of the invention.
* * * * *